Replacement metal gate finfet

ABSTRACT

A method for fabricating a field effect transistor device includes depositing a hardmask over a semiconductor layer depositing a metallic alloy layer over the hardmask, defining a semiconductor fin, depositing a dummy gate stack material layer conformally on exposed portions of the fin, patterning a dummy gate stack by removing portions of the dummy gate stack material using an etching process that selectively removes exposed portions of the dummy gate stack without appreciably removing portions of the metallic alloy layer, removing exposed portions of the metallic alloy layer, forming spacers adjacent to the dummy gate stack, forming source and drain regions on exposed regions of the semiconductor fin, removing the dummy gate stack, removing exposed portions of the metallic alloy layer, and forming a gate stack conformally over exposed portions of the insulator layer and the semiconductor fin.

FIELD OF INVENTION

The present invention relates generally to field effect transistor (FET)devices, and more specifically, to FinFET devices.

DESCRIPTION OF RELATED ART

FinFET devices include an arrangement of fins disposed on a substrate.The fins are formed from a semiconductor material. A gate stack isarranged over the fins and defines a channel region of the fins, whileregions of the fins extending outwardly from the channel region defineactive source and drain regions of the device.

Previous methods for patterning the fins included depositing orthermally growing a hardmask layer of an oxide material over a layer ofsemiconductor material and depositing a lithographic mask over thehardmask layer. The fins are formed by removing exposed portions of thehardmask layer and the semiconductor material resulting in anarrangement of fins having a hardmask layer arranged on thesemiconductor material that is disposed on an insulator layer of thesubstrate.

A dummy gate stack may be formed by depositing a conformal dummy gatematerial over the hardmask layer the fins and the substrate. The dummygate material is patterned using a lithographic etching process todefine a dummy gate stack by removing portions of the dummy gatematerial to expose source and drain regions of the fins. The etchingprocess that removes the dummy gate material removes portions of thehardmask material that protects the semiconductor material in the sourceand drain region of the fins. It is desirable for the hardmask layer tohave a thickness great enough such that the hardmask layer is notcompletely removed from the source and drain regions of the fins duringthe patterning of the dummy gate stack. If the hardmask layer is removedor eroded during the dummy gate etching process, the underlyingsemiconductor material defining the fins may be exposed during the dummygate etching process, which would result in the undesirable removal orlateral erosion of portions of the fins in the source and drain regions.

BRIEF SUMMARY

According to one embodiment of the present invention, a method forfabricating a field effect transistor device includes depositing ahardmask layer over a semiconductor layer, the semiconductor layerdisposed on an insulator layer, depositing a metallic alloy layer overthe hardmask layer, defining a semiconductor fin by patterning andremoving portions of the metallic alloy layer, the hardmask layer, andthe semiconductor layer to expose portions of the insulator layer anddefine the semiconductor fin on the insulator layer, depositing a dummygate stack material layer conformally on exposed portions of theinsulator layer, the semiconductor fin, the hardmask layer and themetallic alloy layer, patterning a dummy gate stack by removing portionsof the dummy gate stack material using an etching process thatselectively removes exposed portions of the dummy gate stack withoutappreciably removing portions of the metallic alloy layer, removingexposed portions of the metallic alloy layer, forming spacers adjacentto the dummy gate stack, forming source and drain regions on exposedregions of the semiconductor fin, removing the dummy gate stack,removing exposed portions of the metallic alloy layer, and forming agate stack conformally over exposed portions of the insulator layer andthe semiconductor fin.

According to another embodiment of the present invention, a method forfabricating a field effect transistor device includes depositing ahardmask layer over a semiconductor layer, the semiconductor layerdisposed on an insulator layer, depositing a metallic alloy layer overthe hardmask layer, defining a semiconductor fin by patterning andremoving portions of the metallic alloy layer, the hardmask layer, andthe semiconductor layer to expose portions of the insulator layer anddefine the semiconductor fin on the insulator layer, forming a mandrelmaterial layer over the metallic alloy layer, patterning and removingportions of the mandrel material layer to expose portions of themetallic alloy layer and define a mandrel arranged on the mandrelmaterial layer, forming mandrel spacers adjacent to the mandrels, themandrel spacers arranged on the metallic alloy layer, removing themandrels to expose portions of the metallic alloy layer, and removingthe portions of the metallic alloy layer, the hardmask layer, and thesemiconductor layer using an etching process that does not appreciablyremove portions of the mandrel spacers, depositing a dummy gate stackmaterial layer conformally on exposed portions of the insulator layer,the semiconductor fin, the hardmask layer and the metallic alloy layer,patterning a dummy gate stack by removing portions of the dummy gatestack material using an etching process that selectively removes exposedportions of the dummy gate stack without appreciably removing portionsof the metallic alloy layer, removing exposed portions of the metallicalloy layer, forming spacers adjacent to the dummy gate stack, formingsource and drain regions on exposed regions of the semiconductor fin,removing the dummy gate stack, removing exposed portions of the metallicalloy layer, and forming a gate stack conformally over exposed portionsof the insulator layer and the semiconductor fin.

According to yet another embodiment of the present invention, a fieldeffect transistor device includes a fin including a semiconductormaterial arranged on an insulator layer, the fin including a channelregion, a hardmask layer arranged partially over the channel region ofthe fin, a gate stack arranged over the hardmask layer and over thechannel region of the fin, a metallic alloy layer arranged on a firstportion of the hardmask layer, the metallic alloy layer arrangedadjacent to the gate stack, and a first spacer arranged adjacent to thegate stack and over the metallic alloy layer.

Additional features and advantages are realized through the techniquesof the present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention. For a better understanding of the invention with theadvantages and the features, refer to the description and to thedrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The subject matter which is regarded as the invention is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The forgoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 illustrates a side view of an exemplary embodiment of asemiconductor-on-insulator (SOI) substrate.

FIG. 2 illustrates the formation of a mandrel layer that is disposed onthe metallic alloy layer.

FIG. 3 illustrates a cut-away view along the line 3 (of FIG. 2).

FIG. 4 illustrates the resultant structure following the deposition of aconformal layer of spacer material.

FIG. 5 illustrates the resultant structure following the removal ofportions of the spacer material.

FIG. 6 illustrates the resultant structure following the removal of themandrels.

FIG. 7 illustrates the resultant structure following anisotropic etchingprocess.

FIG. 8 illustrates the removal of the mandrel spacers.

FIG. 9 illustrates a top view of FIG. 8.

FIG. 10 illustrates a top view of the resultant structure following theformation of a dummy gate stack.

FIG. 11 illustrates a cut-away view along the line 11 (of FIG. 10).

FIG. 12 illustrates a top view of the resultant structure following theremoval of exposed portions of the metallic alloy layer.

FIG. 13 illustrates a top view of the resultant structure following theformation of spacers along sidewalls of the dummy gate stack.

FIG. 14 illustrates a cut-away view along the line 14 (of FIG. 13).

FIG. 15 illustrates a cut-away view along the line 15 (of FIG. 13).

FIG. 16A illustrates a top view of the formation of active regions.

FIG. 16B illustrates a top view of the resultant structure following thedeposition of an oxide layer between the gates and planarization of theoxide layer.

FIG. 17 illustrates a top view of the resultant structure following theremoval of the dummy gate stack.

FIG. 18 illustrates a top view of the resultant structure following theremoval of the exposed metallic alloy material.

FIG. 19 illustrates a top view of the resultant structure following theformation of a gate stack over the channel region of the fins.

FIG. 20 illustrates a cut away view along the line 20 (of FIG. 19).

FIG. 21 illustrates a cut away view along the line 21 (of FIG. 19).

FIG. 22 illustrates a cut away view along the line 22 (of FIG. 19).

FIG. 23 illustrates an alternate exemplary embodiment of a FinFET devicehaving a tri-gate structure.

FIG. 24 illustrates a top view of the resultant structure following theformation of a dummy gate stack.

FIG. 25 illustrates the resultant structure following the formation ofspacers.

FIG. 26 illustrates a cut-away view along the line 26 (of FIG. 25).

FIG. 27 illustrates the removal of exposed portions of the metallicalloy layer following the formation of the spacers.

FIG. 28 illustrates a cut-away view along the line 28 (of FIG. 27).

FIG. 29 illustrates resultant structure following the formation ofsource and drain regions and, the removal of the dummy gate stack, andthe removal of exposed portions of the metallic alloy layer.

FIG. 30 illustrates a cut-away view along the line 30 (of FIG. 29).

FIG. 31 illustrates the formation of a gate stack.

FIG. 32 illustrates the removal of exposed portions of the metallicalloy layer.

FIG. 33 illustrates the resultant structure following the formation ofthe gate stack.

FIG. 34 illustrates another alternate exemplary method and resultantFinFET structure.

FIG. 35 illustrates another alternate exemplary method and resultantstructure.

FIG. 36 illustrates another alternate exemplary method and resultantFinFET structure.

DETAILED DESCRIPTION

Previous methods for patterning a dummy gate stack over fins of a FinFETdevice included patterning fins that included a semiconductor and ahardmask layer disposed thereon. The dummy gate stack was formed bydepositing a dummy gate material over the substrate, fins, and hardmasklayer. The dummy gate stack was patterned using an etching process thatremoves portions of the dummy gate stack material. The semiconductormaterial of the fins was protected by the hardmask layer, which wasdeposited with a thickness such that portions of the hardmask layerwould be removed during the patterning of the dummy gate stack, but somehardmask layer would remain on the fins to prevent an undesirableremoval of the semiconductor material of the fins. Thus, the thicknessof the hardmask layer was partially dependent on the thickness of thedummy gate stack material removed during the dummy gate stack patterningprocess.

As the aspect ratio or height of the dummy gate stack increases, thethickness of the hardmask layer likewise increases to accommodate theetching of a thicker layer of dummy gate stack material and protect theunderlying fins. The use of a thicker hardmask material may becomeproblematic and affect subsequent fabrication processes and theresultant FinFET devices. The methods and resultant structures describedbelow provide for FinFET devices having a high aspect ratio gatestructure, without the use of an undesirably thick hardmask layer.

FIG. 1 illustrates a side view of an exemplary embodiment of asemiconductor-on-insulator (SOI) substrate that includes an insulatorlayer 102 and a semiconductor layer 104 arranged thereon. The insulatorlayer 102 may include, for example a buried oxide (BOX) material.Alternate embodiments my include, an arrangement of the semiconductordevices described herein on a bulk substrate. The semiconductor materialmay include, for example, a silicon or germanium material. A hardmasklayer 106 is disposed on the semiconductor layer 104. The hardmask layer106 may include, for example, an oxide material. A metallic alloy layer108 is disposed on the hardmask layer 106. The metallic alloy layer 108may include, for example, a titanium nitride (TiN), TaN, TiSiN, TaSiN,AlN, AlSiN, TaC, TiC, TiOx, AlxOy, HfOx, or HfSiOx.

FIG. 2 illustrates the formation of a mandrel layer 210 that is disposedon the metallic alloy layer 108. The mandrel material layer 210 mayinclude, for example, amorphous silicon material or a silicon oxidematerial. The mandrel material layer 210 may be formed by, for example,a chemical vapor deposition (CVD) or plasma enhanced chemical vapordeposition (PECVD) process.

FIG. 3 illustrates a cut-away view along the line 3 (of FIG. 2) of theresultant structure following a patterning and etching process thatremoves portions of the mandrel layer 210 using, for example, aphotolithographic patterning and anisotropic etching process such asreactive ion etching (RIE) to form mandrels 302 that are arranged on themetallic alloy layer 108.

FIG. 4 illustrates the resultant structure following the deposition of aconformal layer of spacer material 402 over the mandrels 302 and exposedportions of the metallic alloy layer 108. The spacer material 402 mayinclude, for example, a conformal oxide or nitride material.

FIG. 5 illustrates the resultant structure following the removal ofportions of the spacer material 402 that results in mandrel spacers 502.The mandrel spacers 502 may be formed by, for example, performing ananisotropic etching process that removes portions of the spacer material402, but does not appreciably remove exposed portions of the metallicalloy layer 108 or the mandrels 302.

FIG. 6 illustrates the resultant structure following the removal of themandrels 302. The mandrels 302 may be removed by a suitable etchingprocess that removes the mandrels 302, but does not appreciably removethe mandrel spacers 502 or the exposed portions of the metallic alloylayer 108.

FIG. 7 illustrates the resultant structure following an isotropicetching process, such as for example RIE, to transfer the mandrelpattern into the metallic alloy layer 108, the hardmask layer 106, andthe semiconductor material layer 104. The etching process is selectivesuch that the mandrel spacers 502 are not appreciably removed, and thatremoves exposed portions of the metallic alloy layer 108, the hardmasklayer 106, and the semiconductor material layer 104 to definesemiconductor fins (fins) 702 arranged on the insulator layer 102.

FIG. 8 illustrates the removal of the mandrel spacers 502 (of FIG. 7),which exposes the metallic alloy layer 108. FIG. 9 illustrates atop-view of FIG. 8.

FIG. 10 illustrates a top-view of the resultant structure following theformation of a dummy gate stack 1002 over portions of the fins 702, andFIG. 11 illustrates a cut-away view along the line 11 (of FIG. 10). Inthis regard, a layer of dummy gate stack material such as, for example,polysilicon, is conformably deposited over the insulator layer 102,along the sides of the fins 702, the sides of the hardmask layer 106,and over the metallic alloy layer 108. The dummy gate stack 1002 isformed by, for example, a photolithographic patterning and etchingprocess.

The etching process that patterns the dummy gate stack 1002 includes anisotropic etching process such as, for example, an RIE process that isselective to remove exposed portions of the dummy gate material whilenot appreciably removing exposed portions of the metallic alloy layer108. Thus, the dummy gate stack 1002 may be formed without the use of athick sacrificial layer of hardmask material layer, due to the use of arelatively thin metallic alloy layer 108 and an etch chemistry that isselective to the metallic alloy layer 108.

FIG. 12 illustrates a top-view of the resultant structure following theremoval of exposed portions of the metallic alloy layer 108 (of FIG. 10)using, for example, a selective isotropic etching process that removesthe exposed portions of the metallic alloy layer 108 and exposesportions of the hardmask layer 106.

FIG. 13 illustrates a top-view of the resultant structure following theformation of spacers 1302 along sidewalls of the dummy gate stack 1002.FIG. 14 illustrates a cut-away view along the line 14 (of FIG. 13). FIG.15 illustrates a cut-away view along the line 15 (of FIG. 13). Thespacers 1302 may include, for example, an oxide or nitride material. Thespacers 1302 may be formed by a material deposition and etching process.

FIG. 16A illustrates a top view of the formation of active regions thatinclude a source region 1602 and a drain region 1604. The source anddrain regions 1602 and 1604 may be formed by, for example, an epitaxialgrowth process that grows an epitaxial semiconductor material such as,for example epi-silicon from the exposed portions of the fins 702(described above). The source and drain regions 1602 and 1604 may beformed following the removal of exposed portions of the hardmask layer106 if desired. The source and drain regions 1602 and 1604 may includedopants that may be incorporated in-situ during the epitaxial growthprocess, or implanted in the source and drain regions 1602 and 1604using, for example, an ion implantation process performed following theepitaxial growth process that grows, for example, an epi SiGe(B) on thePFET side, epi Si(P) in the nFET side in a complimentary metal oxidesemiconductor (CMOS) compatible flow.

FIG. 16B illustrates a top view of the resultant structure following thedeposition of an oxide layer 1603 over exposed portions of the sourceregion 1602, the drain region 1604 and the insulator layer 102.Following the deposition of the oxide layer 1603, a planarizing processsuch as, for example, chemical mechanical polishing (CMP) may beperformed to expose the dummy gate stack 1002 and the spacers 1302.

FIG. 17 illustrates a top-view of the resultant structure following theremoval of the dummy gate stack 1002 (of FIG. 16), which exposesportions of the metallic alloy material 108. FIG. 18 illustrates atop-view of the resultant structure following the removal of the exposedmetallic alloy material 108, which exposes portions of the hardmasklayer 106 arranged between the spacers 1302.

FIG. 19 illustrates a top-view of the resultant structure following theformation of a gate stack 1901 over the channel region of the fins 702.FIG. 20 illustrates a cut-away view along the line 20 (of FIG. 19). FIG.21 illustrates a cut-away view along the line 21 (of FIG. 19). FIG. 22illustrates a cut-away view along the line 22 (of FIG. 19). The gatestack 1901 includes a dielectric material layer 1902 that may include,for example, a high-K dielectric material disposed over the hardmasklayer 106 and exposed sidewalls of the fin 702, and a work functionmetal layer 1903 disposed over the dielectric material layer 1902. Ametallic gate material 1904 is disposed over the gate work functionmetal layer 1903. A planarizing process such as, for example, CMP may beperformed to remove overburden material and defined the gate stack 1901following the deposition of the gate dielectric material layer 1902, thework function metal layer 1903, and the metallic gate material 1904.

FIG. 23 illustrates an alternate exemplary embodiment of a FinFET devicehaving a tri-gate structure. In this regard, FIG. 23 shows a similarperspective as FIG. 22. In the embodiment of FIG. 23, the hardmask layer108 (of FIG. 18) is removed using a suitable etching process) prior tothe formation of the gate stack 1901 such that the gate dielectricmaterial layer 1902 contacts the top surface 2301 of the fins 702.

FIGS. 24-31 illustrate an alternate exemplary method and resultantdevice similar to the methods described above. In this regard, similarprocesses as described above in FIGS. 1-11 are performed resulting inthe dummy gate stack 1002 as shown in FIG. 24.

FIG. 25 illustrates the resultant structure following the formation ofspacers 1302 in a similar manner as described above in FIG. 13. FIG. 26illustrates a cut-away view along the line 26 (of FIG. 25). In thisregard, the spacers 1302 are formed prior to the removal of the metallicalloy layer 108 such that the spacers 1302 are formed over portions ofthe metallic alloy material 108.

FIG. 27 illustrates the removal of exposed portions of the metallicalloy layer 108 following the formation of the spacers 1302. FIG. 28illustrates a cut-away view along the line 28 (of FIG. 27).

FIG. 29 illustrates resultant structure following the formation ofsource and drain regions 1602 and 1604, the removal of the dummy gatestack 1002 (of FIG. 28), and the removal of exposed portions of themetallic alloy layer 108 (of FIG. 28) over the channel region of thefins 702. FIG. 30 illustrates a cut-away view along the line 30 (of FIG.29). The exposed portions of the metallic alloy layer 108 have beenremoved using an anisotropic etching process. In the embodimentsdescribed herein, when the hardmask layer 106 remains over portions ofthe fins 702 following fabrication of the device, the hardmask layer 106is formed from an insulating or non-conducting material.

FIG. 31 illustrates the formation of a gate stack 3101 that includes thedielectric layer 1902 and the gate material layer 1904. Portions of themetallic alloy layer 108 remain disposed over portions of the hardmasklayer 106 and are partially covered by the spacers 1302.

FIGS. 32-33 illustrate another exemplary method and resultant structuresimilar to the methods described above in FIGS. 24-31. In this regard,referring to FIG. 32, following the removal of the dummy gate stack asshown above in FIG. 29, the exposed portions of the metallic alloy layer108 are removed using an isotropic etching process that results in theformation of cavities 3201 defined by the spacers 1302 the hardmasklayer 106, and the respective source and drain regions 1602 and 1604.

FIG. 33 illustrates the resultant structure following the formation ofthe gate stack 3301. In this regard the cavities 3201 are filled by thegate dielectric material layer 1902.

FIG. 34 illustrates yet another alternate exemplary method and resultantFinFET structure. In this regard, following the removal of the dummygate stack 1002 (described above), the exposed portions of the metallicalloy layer 108 and the hardmask layer 106 are removed using ananisotropic etching process that exposes a top surface 3402 of thechannel region of the fin 702. A tri-gate gate stack 3401 is formed bydepositing the dielectric layer 1902 and metallic gate material 1094 inthe cavity previously defined by the dummy gate stack 1002.

FIG. 35 illustrates another alternate exemplary method and resultantFinFET structure. In this regard, following the removal of the dummygate stack 1002 (described above), the exposed portions of the metallicalloy layer 108 are removed using an isotropic etching process thatresults in cavities 3502 that are defined by the spacer 1302, a portionof the hardmask layer 106, and the respective source and drain regions1602 and 1604. The exposed portions of the hardmask layer 106 areremoved using an anisotropic etching process that exposes a top surface3402 of the channel region of the fin 702. A tri-gate gate stack 3501 isformed by depositing the dielectric layer 1902 and metallic gatematerial 1904 in the cavity previously defined by the dummy gate stack1002.

FIG. 36 illustrates another alternate exemplary method and resultantFinFET structure. In this regard, following the removal of the dummygate stack 1002 (described above), the exposed portions of the metallicalloy layer 108 and portions of the hardmask layer 106 are removed usingan isotropic etching process that results in cavities 3602 that aredefined by the spacer 1302, a portion of the fin 702, and the respectivesource and drain regions 1602 and 1604. A tri-gate gate stack 3601 isformed by depositing the dielectric layer 1902 and metallic gatematerial 1904 in the cavity previously defined by the dummy gate stack1002.

The methods and resultant structures described herein provide a methodthe fabrication of FinFET devices without using an undesirably thickhardmask layer over the fin structures. The methods also provide for thepatterning of high aspect ratio fins for FinFET devices.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, element components,and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present invention has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the invention in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the invention. Theembodiment was chosen and described in order to best explain theprinciples of the invention and the practical application, and to enableothers of ordinary skill in the art to understand the invention forvarious embodiments with various modifications as are suited to theparticular use contemplated.

The flow diagrams depicted herein are just one example. There may bemany variations to this diagram or the steps (or operations) describedtherein without departing from the spirit of the invention. Forinstance, the steps may be performed in a differing order or steps maybe added, deleted or modified. All of these variations are considered apart of the claimed invention.

While the preferred embodiment to the invention had been described, itwill be understood that those skilled in the art, both now and in thefuture, may make various improvements and enhancements which fall withinthe scope of the claims which follow. These claims should be construedto maintain the proper protection for the invention first described.

What is claimed is:
 1. A method for fabricating a field effecttransistor device, the method comprising: depositing a hardmask layerover a semiconductor layer, the semiconductor layer disposed on aninsulator layer; depositing a metallic alloy layer over the hardmasklayer; defining a semiconductor fin by patterning and removing portionsof the metallic alloy layer, the hardmask layer, and the semiconductorlayer to expose portions of the insulator layer and define thesemiconductor fin on the insulator layer; depositing a dummy gate stackmaterial layer conformally on exposed portions of the insulator layer,the semiconductor fin, the hardmask layer and the metallic alloy layer;patterning a dummy gate stack by removing portions of the dummy gatestack material using an etching process that selectively removes exposedportions of the dummy gate stack without appreciably removing portionsof the metallic alloy layer; removing exposed portions of the metallicalloy layer; forming spacers adjacent to the dummy gate stack; formingsource and drain regions on exposed regions of the semiconductor fin;removing the dummy gate stack; removing exposed portions of the metallicalloy layer; and forming a gate stack conformally over exposed portionsof the insulator layer and the semiconductor fin.
 2. The method of claim1, wherein the patterning and removing the portions of the metallicalloy layer, the hardmask layer, and the semiconductor layer includes:forming a mandrel material layer over the metallic alloy layer;patterning and removing portions of the mandrel material layer to exposeportions of the metallic alloy layer and define a mandrel arranged onthe mandrel material layer; forming mandrel spacers adjacent to themandrels, the mandrel spacers arranged on the metallic alloy layer;removing the mandrels to expose portions of the metallic alloy layer;and removing the portions of the metallic alloy layer, the hardmasklayer, and the semiconductor layer using an etching process that doesnot appreciably remove portions of the mandrel spacers.
 3. The method ofclaim 1, wherein the forming the source and drain regions on the exposedregions of the semiconductor fin includes performing an epitaxial growthprocess.
 4. The method of claim 1, wherein the removing exposed portionsof the metallic alloy layer includes performing an isotropic etchingprocess operative to remove the metallic alloy layer and form a cavitydefined by the spacer, the hardmask layer and the source region.
 5. Themethod of claim 1, wherein the removing exposed portions of the metallicalloy layer includes performing an anisotropic etching process.
 6. Themethod of claim 1, wherein the method further includes, removing exposedportions of the hardmask layer following the removal of the dummy gatestack and the removal of the exposed portions of the metallic alloylayer.
 7. The method of claim 1, wherein the method further includes,removing the exposed portions of the hardmask layer with an anisotropicetching process following the removal of the dummy gate stack and theremoval of the exposed portions of the metallic alloy layer.
 8. Themethod of claim 1, wherein the method further includes, removing theexposed portions of the hardmask layer with an isotropic etching processfollowing the removal of the dummy gate stack and the removal of theexposed portions of the metallic alloy layer.
 9. A method forfabricating a field effect transistor device, the method comprising:depositing a hardmask layer over a semiconductor layer, thesemiconductor layer disposed on an insulator layer; depositing ametallic alloy layer over the hardmask layer; defining a semiconductorfin by patterning and removing portions of the metallic alloy layer, thehardmask layer, and the semiconductor layer to expose portions of theinsulator layer and define the semiconductor fin on the insulator layer;depositing a dummy gate stack material layer conformally on exposedportions of the insulator layer, the semiconductor fin, the hardmasklayer and the metallic alloy layer; patterning a dummy gate stack byremoving portions of the dummy gate stack material using an etchingprocess that selectively removes exposed portions of the dummy gatestack without appreciably removing portions of the metallic alloy layer;forming spacers adjacent to the dummy gate stack; removing exposedportions of the metallic alloy layer; forming source and drain regionson exposed regions of the semiconductor fin; removing the dummy gatestack; removing exposed portions of the metallic alloy layer; andforming a gate stack conformally over exposed portions of the insulatorlayer and the semiconductor fin.
 10. The method of claim 9, wherein thepatterning and removing the portions of the metallic alloy layer, thehardmask layer, and the semiconductor layer includes: forming a mandrelmaterial layer over the metallic alloy layer; patterning and removingportions of the mandrel material layer to expose portions of themetallic alloy layer and define a mandrel arranged on the mandrelmaterial layer; forming mandrel spacers adjacent to the mandrels, themandrel spacers arranged on the metallic alloy layer; removing themandrels to expose portions of the metallic alloy layer; and removingthe portions of the metallic alloy layer, the hardmask layer, and thesemiconductor layer using an etching process that does not appreciablyremove portions of the mandrel spacers.
 11. The method of claim 9,wherein the forming the source and drain regions on the exposed regionsof the semiconductor fin includes performing an epitaxial growthprocess.
 12. The method of claim 9, wherein the removing exposedportions of the metallic alloy layer includes performing an isotropicetching process operative to remove the metallic alloy layer and form acavity defined by the spacer, the hardmask layer and the source region.13. The method of claim 9, wherein the removing exposed portions of themetallic alloy layer includes performing an anisotropic etching process.14. The method of claim 9, wherein the method further includes, removingexposed portions of the hardmask layer following the removal of thedummy gate stack and the removal of the exposed portions of the metallicalloy layer.
 15. The method of claim 9, wherein the method furtherincludes, removing the exposed portions of the hardmask layer with ananisotropic etching process following the removal of the dummy gatestack and the removal of the exposed portions of the metallic alloylayer.
 16. The method of claim 9, wherein the method further includes,removing the exposed portions of the hardmask layer with an isotropicetching process following the removal of the dummy gate stack and theremoval of the exposed portions of the metallic alloy layer.
 17. A fieldeffect transistor device comprising: a fin including a semiconductormaterial arranged on an insulator layer, the fin including a channelregion; a hardmask layer arranged partially over the channel region ofthe fin; a gate stack arranged over the hardmask layer and over thechannel region of the fin; a metallic alloy layer arranged on a firstportion of the hardmask layer, the metallic alloy layer arrangedadjacent to the gate stack; and a first spacer arranged adjacent to thegate stack and over the metallic alloy layer.
 18. The device of claim17, further comprising a source region arranged adjacent to the firstspacer.
 19. The device of claim 17, further comprising: a metallic alloylayer arranged on a second portion of the hardmask layer, the metallicalloy layer arranged adjacent to the gate stack; and a second spacerarranged adjacent to the gate stack and over the metallic alloy arrangedon the second portion of the hardmask layer.
 20. The device of claim 19,comprising a drain region arranged adjacent to the second spacer.